A cost item is an immaterial item that can be added to a product structure or bought and sold. Typical examples may be mileage for service work or cost of documentation or licensing.
In common with other item types, a cost item can have a long description. Descriptions can be in foreign languages that will print with customer facing reports.
A common use of cost items is also for "tagging" work orders with quality issues such as fault codes or rework. To separate out the costs of quality issues in reporting, then set the check box for Quality control.
The fields on cost items generally have the same functionality as material items. Refer to documentation of material items.